JP2014046276A - Ceramic honeycomb structure and method for manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a ceramic honeycomb structure having high performance for removing a harmful substance and high mechanical strength.SOLUTION: In a ceramic honeycomb structure 100, a circumferential groove (groove) 101 having a width along the flow passage direction of Pw and a depth of Ph is formed on a circumference on the outer periphery surface which is a cylindrical surface shape. In addition, the outer surface of an outer peripheral wall 200 is formed into a cylindrical surface shape and the inner surface is formed into a shape fitted to the outer periphery surface of the ceramic honeycomb structure 100. Thus, an inner peripheral projection (projection) 201 fitted to the circumferential groove 101 is formed on the inner surface of the outer peripheral wall 200.

Description

  The present invention relates to a ceramic honeycomb structure used for purification of gas (exhaust gas) and a method for manufacturing the same.

In recent years, diesel engines that have better fuel efficiency and lower CO ₂ emissions than gasoline engines have attracted international attention as engines for automobiles and the like. However, the exhaust gas of diesel engines contains PM (Particulate Matter) and NOx (nitrogen oxides) and other harmful substances, so exhaust gas purification provided in the exhaust system of diesel engines. A ceramic honeycomb structure carrying a catalyst for purifying or removing PM and NOx in exhaust gas is incorporated in the apparatus and used.

  A ceramic honeycomb structure has a large number of elongated channels with a small rectangular cross section partitioned by a porous partition wall having pores made of ceramics. For example, it has a cylindrical shape that is parallel to the longitudinal direction of the flow path (gas flow direction: flow path direction). A catalyst is supported on the surface of the porous partition wall (inner surface of the flow path) and inside the pores.

  FIG. 7A is a perspective view of such a ceramic honeycomb structure, and white arrows indicate the direction in which gas flows (flow path direction). FIG. 7B is a cross-sectional view in the HH direction including a central axis parallel to the flow path direction, and FIG. 7C is a cross-sectional view in the II direction perpendicular to the flow path direction. Moreover, FIG.7 (d) is an enlarged view of the location enclosed with the dotted line in FIG.7 (c).

  As shown in FIG. 7 (a), the outer shape of the ceramic honeycomb structure is cylindrical, and the cross-sectional shape perpendicular to the gas flow (FIG. 7 (c)) is shown in FIG. 7 (d). A large number of such flow paths 20 surrounded by the partition walls 30 are formed. The flow paths 20 are exposed at the circular end faces on the inflow side (upper side in FIGS. 7A and 7B) and the outflow side (same as the lower side), and the gas containing NOx flows from the end face on the inflow side. The gas flows into the channel 20, passes through the elongated channel 20, and the gas flows out from the end surface on the outflow side. As shown in the enlarged view of FIG. 7D, each flow path 20 is configured by partitioning four directions with partition walls 30. The partition wall 30 extends uniformly in the vertical direction in FIG. 7B, and this extended direction becomes the gas flow direction in the flow path 20. As shown in the enlarged view of FIG. 7D, the partition walls 30 are formed in a lattice shape, and a region surrounded by the partition walls 30 is the flow path 20. By supporting the catalyst on the surfaces of the partition walls 30 and inside the pores in the ceramic honeycomb structure, the gas from which harmful substances have been reduced or removed flows out from the end face on the outflow side.

  As shown in FIGS. 7A to 7C, when viewed as a whole, this ceramic honeycomb structure includes a ceramic honeycomb structure body 800 and an outer peripheral wall 900. The ceramic honeycomb structure main body 800 has a cylindrical shape in which the partition walls 30 are integrated as a whole so that the direction in which each flow path 20 extends is parallel to the axial direction of the cylindrical shape. The outer peripheral wall 900 is formed so as to cover a cylindrical outer peripheral surface around the flow path direction in the ceramic honeycomb structure main body 800. When manufacturing this ceramic honeycomb structure, first, the ceramic honeycomb structure main body 800 is manufactured, and the flow path in the outer peripheral portion of the ceramic honeycomb structure main body 800 is processed and removed to form the outer peripheral surface. After the material for forming the outer peripheral wall 900 is applied and formed on the outer peripheral surface of the substrate, it is dried and further baked as necessary, and finally the form shown in FIG. 7 is obtained.

  In recent years, it has been studied to increase the porosity of the partition walls of the honeycomb structure to 45% or more in order to support more catalyst on the honeycomb structure. However, only by increasing the porosity of the partition walls of the honeycomb structure, although the catalyst supporting characteristics can be improved, it is difficult to ensure the necessary strength of the honeycomb structure.

  On the other hand, in order for the catalyst supported on the partition walls 30 to be activated and function, it is necessary that the catalyst supported inside the ceramic honeycomb structure has a high temperature. For this reason, it is necessary for the temperature inside the ceramic honeycomb structure to rise in a short time after the hot gas flows through the flow path after the engine is started.

  In the technique described in Patent Document 1, in order to improve the strength of the honeycomb structure on the exhaust gas discharge side, the thickness of the outer peripheral wall at one end and the other end in the gas flow direction is different, The wall is thicker than the outer peripheral wall on the other end side. At this time, the cross-sectional area of the flow path on one end side can be made smaller than the cross-sectional area of the flow path on the other end side so that the outer diameter of the outer peripheral wall is the same on one end side and the other end side. It is described that the cross-sectional area of the passage is equal to the cross-sectional area of the flow path on the other end side, and the outer diameter of the outer peripheral wall on one end side can be made larger than that on the other end side.

  In the technique described in Patent Document 2, for example, a circular concave portion is partially formed on the cylindrical outer peripheral surface of the ceramic honeycomb structure body, and a coating layer is coated on the outer peripheral surface and the concave portion, so that the outer peripheral wall is formed. The forming technique is described. It is described that this configuration suppresses peeling between the outer peripheral wall and the coating layer.

JP 2008-215337 A JP 2007-290945 A

  In the ceramic honeycomb structure having the configuration described in Patent Document 1, the thickness of the outer peripheral wall at one end and the other end is different, and the strength of the outer peripheral wall is low because the thickness of the outer peripheral wall at one end is thin. Since the outer peripheral wall is thick at the end, it is difficult for the temperature of the honeycomb structure to rise due to the exhaust gas, and it takes time until the catalyst is activated after the engine is started, and there is a problem in the harmful substance removal performance. It was.

  In the ceramic honeycomb structure having the configuration described in Patent Document 2, since the coating layer is coated on the surface of the outer wall, heat is not easily transmitted between the two, and the thickness of the outer peripheral wall itself is also increased. It took time until the catalyst was activated after the engine was started, and there was a problem in the performance of removing harmful substances.

  The present invention has been made in view of such problems, and achieves both high mechanical strength and high harmful substance removal performance even when the porosity of the partition walls of the honeycomb structure is as high as 45% or more. An object of the present invention is to provide a ceramic honeycomb structure that can be manufactured and a method for manufacturing the same.

In order to solve the above problems, the present invention has the following configurations.
A ceramic honeycomb structure of the present invention includes a ceramic honeycomb structure main body having a configuration in which a plurality of flow paths configured by being partitioned by a partition made of porous ceramics are provided adjacently in parallel, and A ceramic honeycomb structure including an outer peripheral wall formed to cover an outer peripheral surface around a flow path direction in the ceramic honeycomb structure main body, wherein the outer peripheral surface of the ceramic honeycomb structure main body is located at an outermost periphery The flow path that opens to the outside without having a partition wall between the outside, a groove that is continuous in the circumferential direction of the outer peripheral surface is formed, and a protrusion that fits the groove on the inner surface of the outer peripheral wall The porosity of the ceramic constituting the partition wall is in the range of 45 to 70%, the thickness of the partition wall is in the range of 0.1 to 0.4 mm, and the portion other than the portion where the protrusion is formed. The thickness of the outer peripheral wall is in the range of 0.1 to 5.0 mm, and the sum of the widths of the grooves along the flow direction is L / 300 to L as the length of the ceramic honeycomb structure in the flow path direction. It is the range of L / 10.
In the ceramic honeycomb structure of the present invention, the groove and the protrusion are formed at a plurality of locations in the flow path direction.
In the ceramic honeycomb structure of the present invention, the groove and the protrusion are formed in a region where the distance from the end in the flow channel direction of the ceramic honeycomb structure is 0.2 L or more. .
The method for manufacturing a ceramic honeycomb structure according to the present invention is a method for manufacturing the ceramic honeycomb structure, comprising: a formed body forming step for forming a formed body having a honeycomb structure; and a sintered body obtained by firing the formed body. A firing step, a processing step of removing an outer peripheral edge of the sintered body, a groove processing step of forming the groove on the outer peripheral surface of the sintered body, and a material to be the outer peripheral wall with the outer peripheral surface and And an outer peripheral wall forming step of forming the outer peripheral wall by drying and / or baking after being applied to the groove.
The method for manufacturing a ceramic honeycomb structure according to the present invention is a method for manufacturing the ceramic honeycomb structure, the forming body forming step for forming a formed body having a honeycomb structure, and the processing for removing the peripheral edge of the formed body. A step of firing the formed body to form a sintered body, a groove processing step of forming the groove on the outer peripheral surface of the sintered body, and a material for the outer peripheral wall as the outer peripheral surface and the And an outer peripheral wall forming step of forming the outer peripheral wall by drying and / or baking after being applied to the groove.
The method for manufacturing a ceramic honeycomb structure according to the present invention is a method for manufacturing the ceramic honeycomb structure, the forming body forming step for forming a formed body having a honeycomb structure, and the processing for removing the peripheral edge of the formed body. A step of forming a groove on the outer peripheral surface of the molded body, a firing step of firing the molded body to form a sintered body, and a material for the outer peripheral wall as the outer peripheral surface and the groove. And an outer peripheral wall forming step in which the outer peripheral wall is formed by drying and / or baking after being applied to the substrate.

  Since the present invention is configured as described above, a ceramic honeycomb structure that can achieve both high mechanical strength and high harmful substance removal performance can be obtained.

The perspective view (a) of the ceramic honeycomb structure which concerns on embodiment of this invention, the schematic cross section (b) along the flow path direction, the schematic cross section (c) of the AA direction, BB It is a schematic cross section (d) of a direction. 1 is a perspective view of a ceramic honeycomb structure body (a) and an outer peripheral wall (b) in a ceramic honeycomb structure according to an embodiment of the present invention. It is a figure which shows typically the form in the case of the outer peripheral wall formation process in the manufacturing method of the ceramic honeycomb structure which concerns on embodiment of this invention. It is a schematic cross section along the flow path direction of a modified example of the ceramic honeycomb structure according to the embodiment of the present invention. 1 is a schematic cross-sectional view of a ceramic honeycomb structure as an example. It is a schematic cross section of a ceramic honeycomb structure as a comparative example. A perspective view (a) of a conventional ceramic honeycomb structure, a schematic cross-sectional view (b) along the flow path direction, a schematic cross-sectional view (c) perpendicular to the flow path direction, and an enlarged view of a cross section perpendicular to the flow path direction ( d).

  The present invention will be described below with reference to specific embodiments. However, the present invention is not limited to these embodiments. The ceramic honeycomb structure of the present invention includes a ceramic honeycomb structure main body and an outer peripheral wall that covers the outer peripheral surface and mechanically reinforces the ceramic honeycomb structure main body.

  FIG. 1A is a perspective view of a ceramic honeycomb structure according to an embodiment of the present invention, and gas flows in the direction of the white arrow (vertical direction in the figure) in this ceramic honeycomb structure. FIG.1 (b) is sectional drawing along the flow-path direction on the central axis. FIG.1 (c) is sectional drawing of the AA direction (area | region above a center part in FIG.1 (b)), FIG.1 (d) is the BB direction (FIG.1 (b)). It is sectional drawing of the center part in the up-down direction. As shown here, the ceramic honeycomb structure includes a substantially cylindrical ceramic honeycomb structure main body 100 and an outer peripheral wall 200. The ceramic honeycomb structure main body 100 has a substantially cylindrical shape as a whole, in which a large number of flow paths along the central axis direction of the cylindrical shape are integrated in parallel. The structure of the flow path in the ceramic honeycomb structure main body 100, that is, each flow path is configured by partitioning four directions with partition walls is the same as the structure shown in FIG.

  2A is a perspective view of the ceramic structure body 100 (a) in a state corresponding to FIG. 1A, and FIG. 2B is a perspective view showing the shape of the outer peripheral wall 200 (b). It is. As shown in FIGS. 1 and 2, the outer peripheral surface of the ceramic honeycomb structure body 100 has an outer peripheral surface in which a channel located on the outermost periphery does not have a partition wall between the outer periphery and the outer peripheral surface. A circumferential groove (groove) 101 having a width Pw and a depth Ph along the flow path direction is formed on the circumference. Further, the outer surface of the outer peripheral wall 200 has a cylindrical surface shape, and the inner surface thereof has a shape that fits with the outer peripheral surface of the ceramic honeycomb structure body 100. For this reason, an inner peripheral projection (projection) 201 that fits with the circumferential groove 101 is formed on the inner surface of the outer peripheral wall 200. The width along the flow path direction of the inner peripheral projection 201 and the height perpendicular to the flow path direction correspond to the circumferential groove 101 and are Pw and Ph, respectively. The thickness of the outer peripheral wall 200 other than the inner peripheral protrusion 201 is uniform, and the thickness is T. The outer peripheral wall thickness T refers to the thickness from the outermost peripheral surface where the channel located at the outermost periphery does not have a partition wall between the outer periphery and opens to the outside. In addition, since the circumferential groove 101 is formed in the ceramic honeycomb structure main body 100 in which the flow path 20 is uniformly formed, the portion where the circumferential groove 101 is formed in FIG. Although the flow path 20 may be exposed, this description is omitted here. The exposed flow path 20 is blocked by the outer peripheral wall 200.

  In addition, as described above, the outer peripheral wall 200 actually has an outer peripheral wall 200 on the outer peripheral surface where the flow path located on the outermost periphery of the ceramic honeycomb structure main body 100 does not have a partition wall between the outside and opens to the outside. It is formed by applying and then drying and / or firing.

The ceramic honeycomb structure main body 100 is configured such that the partition walls 30 are integrated to form the entire shape shown in FIG. The material constituting the partition wall 30 is cordierite (2MgO · 2Al ₂ O ₃ · 5SiO ₂ ), alumina (Al ₂ O ₃ ), mullite (3Al ₂ O ₃ · 2SiO ₂ ), silicon nitride (Si ₃ N _4). ), LAS (Li ₂ O.Al ₂ O ₃ .SiO ₂ ), ceramics such as aluminum titanate can be used. In this case, add organic binder such as methylcellulose, hydroxypropylmethylcellulose, lubricant and pore former to the mixed powder of these raw materials, mix thoroughly by dry method, add specified amount of water, and knead sufficiently. It can be made into a clay that can be plasticized to form a molded body.

For example, when cordierite is used as the material of the partition wall 30, kaolin, calcined kaolin, alumina, aluminum hydroxide, silica, talc, etc. are composed of 12 to 16% MgO, Al ₂ O _{3 in} the composition after firing. Is 30 to 45%, and SiO ₂ is mixed so as to have a mass ratio of about 42 to 56%. To this, a binder and a sintering aid are appropriately added to obtain a raw material powder.

  As the pore former, graphite, carbon powder, wheat flour, corn starch, resin, unfoamed hollow resin, foamed hollow resin, or the like can be used. Among them, it is preferable to use particles of a hollow resin material made of polymethyl methacrylate, polybutyl methacrylate, polyacrylate ester, polystyrene, polyacryl ester, polyethylene, polyethylene terephthalate, methyl methacrylate / acrylonitrile copolymer and the like. At this time, it is preferable to enclose a gas such as hydrocarbon, have an outer shell thickness of about 0.1 to 2 μm, an average particle diameter of 20 to 70 μm, and a moisture content of about 70 to 95%.

  When the pore former is added to the above raw material powder, for example, by a hollow resin at a mass ratio of about 5 to 10%, and after forming a clay, it is molded and fired at about 1410 ° C., the porosity is 45 to 70. % Can be increased. At this time, the volume ratio of small pores having a pore diameter of 20 μm or less can be 20% or less, and the volume ratio of large pores having a pore diameter of 50 μm or more can be 20% or less. As a result, a large amount of catalyst can be supported on the surface of the ceramic (partition wall 30) or in the pores therein.

  When manufacturing the ceramic honeycomb structure body 100 having the shape shown in FIG. 2A, first, a molded body corresponding to the ceramic honeycomb structure body (FIG. 7) is manufactured by extruding the above-mentioned clay. (Molded body forming step). Since this structure is uniform in the vertical direction (flow channel direction) in FIG. 7, it can be manufactured by extrusion molding. Then, this shaped body is fired at the above temperature to obtain a sintered body of this shape (firing step). Next, the peripheral peripheral edge of the cylindrical surface shape in this sintered body is processed and removed with a lathe, and the flow path located on the outermost periphery has an outer peripheral surface opened to the outside without having a partition wall between the outside (processing) Process). Next, the outer peripheral surface of the sintered body is processed by, for example, a lathe or a cylindrical grinder to form the circumferential groove 101 (groove processing step). The process of forming the circumferential groove 101 over the circumference can be performed particularly easily by rotating the sintered body around the central axis. Thereby, the ceramic honeycomb structure main body 100 in the form of FIG. 2A can be obtained.

In addition, as long as said structure can be obtained, the order which performs a process process, a baking process, and a groove process process can be set suitably. For example, the order of the firing step, the processing step, the groove processing step, the processing step, the firing step, the order of the groove processing step, the order of the processing step, the groove processing step, and the firing step can be used. When performing in order of a baking process, a process process, and a groove process, a process process and a groove process are performed with respect to a sintered compact. When performing in order of a processing process, a baking process, and a groove processing process, a processing process is performed with respect to the molded object before baking, and a groove processing process is performed with respect to a sintered compact. When performing in order of a processing process, a groove processing process, and a baking process, a processing process and a groove processing process are performed with respect to the molded object before baking. Therefore, the order in which these steps are performed can be appropriately set according to the material constituting the ceramic honeycomb structure body 100 (partition wall 30), its structure, the shape of the circumferential groove, and the like.

  The outer peripheral wall 200 is formed by applying a material to be the outer peripheral wall 200 to the outer peripheral surface and the groove and then drying and / or firing the ceramic honeycomb structure body 100 after the grooving process (outer periphery). Wall formation process). The outer peripheral wall 200 is obtained, for example, by applying and baking a paste-like material in which ceramic particles, colloidal silica or colloidal alumina, a binder, water, and a dispersant as necessary are mixed. In this case, as the ceramic particles, a ceramic material similar to that of the ceramic honeycomb structure body 100 can be used. For example, cordierite, alumina, mullite, silica, aluminum titanate, or the like can be used.

  FIG. 3 is a diagram schematically showing a form when a material to be the outer peripheral wall 200 is applied. Here, support plate 500a, 500b in which the end surface 100a on the inflow side and the end surface 100b on the outflow side of the ceramic honeycomb structure main body 100 after the grooving step have a larger outer diameter than the end surface of the ceramic honeycomb structure main body 100. Each is sandwiched and supported and fixed. In this state, the flat scraper 550 is installed so as to contact the upper support plate outer peripheral ends 510a and 510b of the support plates 500a and 500b, so that the upper end portion of the ceramic honeycomb structure body 100 and the scraper 550 are placed. A gap is formed between the two. In this state, the gap between the upper end portion of the ceramic honeycomb structure main body 100 and the flat scraper 550 is filled with the coating material 210 made of the above components and used as the raw material of the outer peripheral wall 200. Thereafter, if the ceramic honeycomb structure main body 100 and the support plates 500a and 500b are rotated about the central axis X, the coating material 210 is uniform over the entire surface of the ceramic honeycomb structure main body 100 except for the circumferential grooves 101. It is applied in various thicknesses. At this time, the circumferential groove 101 is also filled with the coating material 210. Thereafter, by firing, the outer peripheral wall 200 having the inner peripheral protrusion 201 and having sufficient mechanical strength can be obtained.

  In the ceramic honeycomb structure having this configuration, the inner peripheral protrusion 201 that is particularly thick is formed on the outer peripheral wall 200 that mechanically reinforces the structure, so that the mechanical strength can be increased. At this time, since the inner peripheral protrusion 201 is formed over the entire area in the circumferential direction (around the flow path direction), the mechanical strength can be increased. Further, since the inner peripheral projection 201 is locally formed along the gas flow direction, an increase in the heat capacity of the entire ceramic honeycomb structure can be suppressed, and the time required for activation of the catalyst is shortened. High harmful substance removal performance can be obtained.

  Here, as described above, in particular, when the partition wall 30 is loaded with a large amount of catalyst and the partition wall 30 is thinned to secure the area of the flow path 20, the mechanical strength of the ceramic honeycomb structure is increased by the above configuration. Increasing the height is particularly effective. Specifically, the porosity of the porous ceramics constituting the partition wall 30 in such a case is in the range of 45 to 70%, and the thickness t (FIG. 7 (d)) of the partition wall 30 is in the range of 0.1 to 0.4 mm. It is.

  When the thickness t of the partition wall 30 is less than 0.1 mm, the mechanical strength is insufficient, and when it exceeds 0.4 mm, the pressure loss increases. The thickness t of the partition wall 30 is particularly preferably in the range of 0.15 to 0.35 mm.

  In addition, when the porosity of the porous ceramic is less than 45%, the amount of the supported catalyst may be insufficient, and thus it may be difficult to obtain sufficient harmful substance removal performance. When the porosity exceeds 70% Therefore, the mechanical strength of the partition wall 30 or the ceramic honeycomb structure is insufficient. The porosity is more preferably 50 to 65%, and particularly preferably 55 to 65%.

  The thickness T of the outer peripheral wall 200 combined with the ceramic honeycomb structure main body 100 having such a configuration is in the range of 0.1 to 5.0 mm, and the height Ph of the inner peripheral protrusion 201 is equal to T. The range is 0.0 mm. Further, the width Pw along the flow path direction of the inner peripheral protrusion 201 is set to a range of L / 300 to L / 10, where L is the length of the ceramic honeycomb structure in the flow path direction. When T is less than 0.1 mm, Ph is less than 0.1 mm, and Pw is less than L / 300, the mechanical strength of the ceramic honeycomb structure is insufficient. When T exceeds 5.0 mm, when Ph exceeds 5.0 mm, or when Pw exceeds L / 10, the pressure loss increases or the heat capacity increases. It takes a long time to complete. T and Ph are more preferably in the range of 0.5 to 4.0, and Pw is more preferably in the range of L / 150 to L / 15. T and Ph are in the range of 1.0 to 3.0, and L / 100 to L / 20. More preferably.

  As shown in the cross-sectional view of FIG. 5, it is preferable to form the inner peripheral projections in a plurality of rows instead of one row. Even in such a case, since the outer peripheral wall in the portion where the circumferential groove (inner peripheral protrusion) is not formed is thinned with a thickness T, the heat capacity of this portion is small, so that when the gas is flowed, The temperature rises and the catalytic reaction easily occurs in this part. On the other hand, it is clear that the mechanical strength of the entire ceramic honeycomb structure increases as the number of circumferential grooves (inner peripheral projections) increases. For this reason, even when a plurality of circumferential grooves (inner peripheral protrusions) are formed, both high harmful substance removal performance and high mechanical strength can be achieved.

The number of channels 20 per unit area in the cross section perpendicular to the channel direction of the ceramic honeycomb structure body 100 is preferably in the range of 15 to 70 / cm ² . When the surface density is less than 15 / cm ² , the reaction by the catalyst becomes insufficient. When it exceeds 70 pieces / cm ² , the area of the flow path 20 becomes small, so that the pressure loss when the gas flows is increased. The number of flow paths 20 per unit area is particularly preferably in the range of 20 to 60 / cm ² .

  Moreover, the cross-sectional shape of the circumferential groove 101 or the inner circumferential protrusion 201 is arbitrary. For example, in FIG. 4 (a), the cross-sectional view of the ceramic honeycomb structure may be triangular as shown in FIG. 1 (b), and as shown in FIG. 4 (b), The cross-sectional shape can be an arc shape. Regardless of the cross-sectional shape, the cross-sectional groove is formed on the surface of the formed body or sintered body corresponding to the ceramic honeycomb structure body before the circumferential groove 101 is formed (grooving step). The ceramic honeycomb structure body 100 described above can be obtained. Thereafter, by forming the outer peripheral wall 200 (outer peripheral wall forming step), the inner peripheral protrusion 201 having these cross-sectional shapes can be formed.

  In places other than the place where the circumferential groove 101 and the inner peripheral projection 201 are formed, it is preferable to make the outer peripheral wall 200 thinner to reduce the heat capacity and shorten the time required for activation of the catalyst. For this reason, for example, a configuration in which the circumferential groove 101 (inner peripheral protrusion 201) is locally formed on the outer peripheral surface of the ceramic honeycomb structure body 100 and the outer peripheral wall 200 is thinned as a whole is preferable. On the other hand, for example, the shape shown in FIG. 6D in which the outer peripheral wall is thick at the center in the flow path direction and the outer peripheral wall is gradually thinned on both sides thereof increases the heat capacity. Is unpreferable because it becomes longer.

  1 and 4, the circumferential groove 101 (inner peripheral protrusion 201) is provided at the center in the flow path direction. Such a configuration is particularly effective in that the mechanical strength of the entire ceramic honeycomb structure is increased because the central portion in the flow path direction is particularly reinforced. However, it is not necessary to provide the circumferential groove 101 (inner circumferential protrusion 201) strictly at the center in the flow path direction. However, in order to increase the mechanical strength of the entire ceramic honeycomb structure, it is preferable to provide the circumferential groove 101 (inner peripheral protrusion 201) at least near the center and particularly reinforce the vicinity of the center. For this reason, it is preferable to form the circumferential groove 101 (inner peripheral protrusion 201) in a region where the distance from the end in the flow channel direction of the ceramic honeycomb structure is 0.2 L or more. Here, this distance is defined as the distance from the end to the apex of the inner peripheral projection 201. This is the same even when a plurality of rows of circumferential grooves (inner circumferential protrusions) are provided. That is, when a plurality of circumferential grooves (inner circumferential protrusions) are provided, it is preferable that at least one of the circumferential grooves is formed in a region having a distance of 0.2 L or more from the end.

(Example)
Actually, a plurality of types of ceramic honeycomb structures having a combination of a ceramic honeycomb structure main body and an outer peripheral wall are manufactured, a catalyst is formed inside, (1) breaking strength in hydrostatic pressure test, (2) up to catalyst activity Time, (3) thermal shock temperature was measured.

Here, the ceramic honeycomb structures to be examples 1 to 6 and comparative examples 1 to 4 were manufactured. As described above, the sintered body after being fired in a cylindrical shape (a state in which no circumferential groove is formed) A circumferential groove was formed on the surface by a lathe. The sintered body before grooving had an outer diameter of 264 mm and an axial length L of 304.8 mm, and all of Examples 1 to 12 and Comparative Examples 1 to 8 were the same. At this time, the partition wall thickness t was set to the value shown in Table 1, and the partition wall pitch was 1.5 mm. The material constituting the partition walls (ceramic honeycomb structure) is a ceramic using a cordierite forming raw material powder formed by blending raw material powders of silica, kaolin, talc, alumina, and aluminum hydroxide. The raw material powder composition was 51% by mass of SiO ₂ , 35% by mass of Al ₂ O ₃ and 14% by mass of MgO. Hollow resin particles made of methylcellulose and hydroxypropylmethylcellulose as the organic binder and acrylonitrile copolymer as the pore former were used, and the addition amount of the pore former was adjusted to the porosity shown in Table 1. The firing temperature was 1400 ° to obtain a cordierite ceramic honeycomb structure. Then, after the surface processing according to each sample was performed (groove processing step), the outer peripheral wall made of silica was formed by the outer peripheral wall forming step. The conditions other than the shape of the groove (the outer peripheral surface of the ceramic honeycomb structure main body) in the groove processing step and the conditions in the outer peripheral wall forming step were all the same.

  The cross-sectional shape of Example 1 is as shown in FIG. 4 (a), Examples 2 and 13, and Comparative Example 9 are as shown in FIG. 4 (b). It is as shown in 5 (a) to (f). The cross-sectional shapes of Comparative Examples 1 to 4 are as shown in FIGS. 6 (a) to 6 (d), respectively. The cross-sectional shapes of Examples 9 to 12 and Comparative Examples 5 to 8 and 10 are all as shown in FIG. In Examples 3 to 5, the inner peripheral protrusions are periodically formed in four rows, and the cross-sectional shape of the inner peripheral protrusions is triangular in Example 3, rectangular in Example 4, and circular arc in Example 5. In both cases, Pw = 2.0 mm and Ph = 2.0 mm.

In Example 6, the interval between the inner peripheral projections in Example 5 was increased, and the flow path was inclined by 0.6 ° from the cylindrical central axis. Such a shape in which the flow path deviates from the central axis of the cylindrical shape is a form that can occur particularly when mass-producing a ceramic honeycomb structure. In Examples 7 and 8, the inner peripheral projections in the configuration of Example 5 were arranged in 5 rows and 6 rows, respectively. In each of Examples 1 to 8, the thickness T of the outer peripheral wall at a location where there was no inner peripheral protrusion was 1.0 mm.

  Comparative Examples 1 and 3 have the structure shown in FIG. 7 (Comparative Example 1: T = 1.0 mm, Comparative Example 3: T = 3.0 mm) in which no inner peripheral protrusion is formed (circumferential groove is not formed). . In Comparative Example 2, the outer peripheral wall had a maximum thickness (3 mm) at the upper and lower ends and a minimum thickness (1 mm) at the center (a thick configuration at both ends). In Comparative Example 4, instead of providing a local groove on the surface of the ceramic honeycomb structure main body, the entire structure is gradual and the outer peripheral wall is thick at the center (thin at the center), and T = 1.0 mm, T = 3.0 mm at the center. The forms of Comparative Examples 5 to 8 are the same as those of Examples 9 to 12, but Comparative Examples 5 and 6 have a porosity outside the range of 45 to 70%, and Comparative Examples 7 and 8 have a partition wall thickness t. It was outside the range of 0.1 to 0.4 mm. In Comparative Examples 9 and 10, the total Pw was outside the range of L / 300 to L / 10.

  Table 1 shows the values of the parameters in Examples and Comparative Examples, and Table 2 shows the evaluation results.

  Isostatic strength (1) was measured as the breaking strength when hydrostatic pressure was applied to the ceramic honeycomb structure. Here, when the strength exceeds 1.0 kPa, ◎, when 1.0 kPa or less and 0.6 kPa, ○, when 0.6 kPa or less and more than 0.4 kPa, Δ,. The case of 4 kPa or less was set as x.

  As time (2) until catalyst activity, the catalyst was applied in the flow path of the ceramic honeycomb structure, and the time until the catalyst was activated was measured. Using this time in Comparative Example 1 as a reference, the case where it was 5% or more shorter than this, ◎ less than 5%, 2% or more shorter, ○ less than 2%, 0 or shorter, Δ, longer The case was marked with x.

  Here, the thermal shock temperature (3) was rapidly cooled to room temperature (25 ° C.) after the ceramic honeycomb structure was put in an electric furnace controlled to a constant heating temperature (500 ° C. or higher), heated and held for 30 minutes. And the temperature difference between the heating temperature and the room temperature when a crack is discovered. The case where this temperature difference was 650 ° C. or higher was rated as “◎”, the case where it was lower than 650 ° C. and 600 ° C. or higher, “O”, the case where it was lower than 600 ° C. and 550 ° C. or higher,

  From the above, it was confirmed that the ceramic honeycomb structure as an example can obtain high thermal shock resistance, mechanical strength, and high harmful substance removal performance.

  In the above example, the cross-sectional shape of the flow path is rectangular, but similarly, a configuration in which a large number of flow paths partitioned by partition walls can be stacked, for example, the cross-sectional shape of the flow path is a regular triangle or a regular hexagon. The same applies to the case of the above.

  In the above example, the outer diameter of the cross-sectional shape perpendicular to the flow path direction of the ceramic honeycomb structure is circular (the ceramic honeycomb structure is cylindrical), but the cross-sectional shape is not necessarily circular. It is clear that the same effect can be obtained.

  Moreover, in the above example, the example of the ceramic honeycomb structure has been described. However, two flow paths in which one end is sealed are formed adjacent to each other, and the partition between the flow paths is a filter. The above-described invention can also be applied to a ceramic honeycomb filter used as the above. Further, in the above example, as a flow path having a substantially polygonal cross-sectional shape, a quadrangular cross-section flow path is mainly described, but the above-described invention also applies to a cross-sectional flow path such as a triangle, hexagon, or octagon. Can also be applied.

20 Channel 30 Partition 100, 800 Ceramic honeycomb structure body 100a Inflow side end surface 100b Outflow side end surface 101 Circumferential groove (groove)
200, 900 Outer peripheral wall 201 Inner peripheral protrusion (protrusion)
210 Coating material 500a, 500b Support plate 510a, 510b Support plate outer peripheral end 550 Scraper

Claims (6)

A ceramic honeycomb structure body having a configuration in which a plurality of flow paths configured by being divided by partition walls made of porous ceramics are provided adjacent to each other in parallel, and a flow path direction in the ceramic honeycomb structure main body An outer peripheral wall formed to cover an outer peripheral surface around the ceramic honeycomb structure,
The outer peripheral surface of the ceramic honeycomb structure body has an opening to the outside without a partition wall between the outside and the flow path located at the outermost periphery,
A continuous groove is formed in the circumferential direction of the outer peripheral surface,
Protrusions that fit into the grooves are formed on the inner surface of the outer peripheral wall,
The thickness of the outer peripheral wall except for the portion where the porosity of the ceramic constituting the partition wall is in the range of 45 to 70%, the thickness of the partition wall is in the range of 0.1 to 0.4 mm, and the protrusion is formed. Is in the range of 0.1 to 5.0 mm, and the total width of the grooves along the flow direction is L / 300 to L / 10, where L is the length of the ceramic honeycomb structure in the flow path direction. The ceramic honeycomb structure characterized by the above-mentioned. The ceramic honeycomb structure according to claim 1, wherein the groove and the protrusion are formed at a plurality of locations in the flow path direction.
3. The ceramic according to claim 1, wherein the groove and the protrusion are formed in a region having a distance of 0.2 L or more from the end in the flow channel direction of the ceramic honeycomb structure. Honeycomb structure.
A method for manufacturing a ceramic honeycomb structure according to any one of claims 1 to 3,
A molded body forming step of forming a molded body having a honeycomb structure;
A firing step of firing the molded body to obtain a sintered body;
A processing step of removing the outer peripheral edge of the sintered body;
A groove processing step of forming the groove on the outer peripheral surface of the sintered body;
An outer peripheral wall forming step of forming the outer peripheral wall by applying the material to be the outer peripheral wall to the outer peripheral surface and the groove and then drying and / or firing.
A method for manufacturing a ceramic honeycomb structure, comprising: A method for manufacturing a ceramic honeycomb structure according to any one of claims 1 to 3,
A molded body forming step of forming a molded body having a honeycomb structure;
A processing step of removing the peripheral edge of the molded body;
A firing step of firing the molded body to obtain a sintered body;
A groove processing step of forming the groove on the outer peripheral surface of the sintered body;
An outer peripheral wall forming step of forming the outer peripheral wall by applying the material to be the outer peripheral wall to the outer peripheral surface and the groove and then drying and / or firing.
A method for manufacturing a ceramic honeycomb structure, comprising: A method for manufacturing a ceramic honeycomb structure according to any one of claims 1 to 3,
A molded body forming step of forming a molded body having a honeycomb structure;
A processing step of removing the peripheral edge of the molded body;
A groove processing step of forming the groove on the outer peripheral surface of the molded body;
A firing step of firing the molded body to obtain a sintered body;
An outer peripheral wall forming step of forming the outer peripheral wall by applying the material to be the outer peripheral wall to the outer peripheral surface and the groove and then drying and / or firing.
A method for manufacturing a ceramic honeycomb structure, comprising:

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